1. Field of the Invention
The present invention relates to: a mechanism for electrification (e.g., grounding) of a rotating body used in any of an electrophotographic image forming apparatus, an electrostatic-recording image forming apparatus, and a magnetic-recording image forming apparatus; an image carrier unit, a process cartridge, and an image forming apparatus using the mechanism for the rotating body; and a method for electrifying (e.g., grounding) an image carrier unit.
2. Description of the Related Art
There have been proposed technologies for electrification, such as grounding, using a conductive cloth or static eliminating cloth having the conductive property and flexibility, a conductive sheet, or a metal leaf spring in a mechanism for electrification, such as grounding, of a rotating body used in an electrophotographic image forming apparatus, such as a copier, a facsimile machine, a printer, a plotter, or a multifunction peripheral having a plurality of such functions (for example, see Japanese Patent Application Laid-open No. 2000-48873, Japanese Patent Application Laid-open No. 2007-57945, Japanese Patent Application Laid-open No. H11-249495, Japanese Patent No. 3950635, and Japanese Patent No. 3938273).
Japanese Patent Application Laid-open No. 2000-48873 discloses a grounding device for a conductive rotary shaft that is used in a sheet conveying apparatus. The grounding device includes a grounding unit having a core made of an elastic material and a conductive material (a cloth, hereinafter referred to as a “conductive cloth”) formed around the core. A conductive surface of the grounding unit is biased against the surface of the conductive shaft that is rotating, and another conductive surface of the grounding unit is brought into contact with a conductive member that is electrically connected to the grounded frame of the main body of the grounding device, so that the conductive shaft that is rotating is grounded.
Japanese Patent Application Laid-open No. 2007-57945 discloses a technique of achieving the grounding by the use of a static eliminating member, which is provided near a transfer unit to eliminate the static of a recording medium. The static eliminating member uses a static eliminating cloth (conductive cloth) made of a sheet-like conductive fiber aggregate as a base material. The static eliminating cloth is attached to a member and comes into press contact with the member while it is moved in synchronization with the member, so that grounding is achieved.
Japanese Patent Application Laid-open No. H11-249495 discloses a structure including a shaft contact spring (first leaf spring) of a drum grounding plate that comes into contact with an electrical connection shaft by which a photosensitive drum (cylindrical member) is rotatably supported, and two or more grounding spring contact parts (second leaf springs) of cylinder springs and that come into contact with an inner wall of the photosensitive drum, in which the electrical connection shaft and the inner wall of the photosensitive drum are electrically connected to each other (see FIGS. 4 and 20 to 24 of Japanese Patent Application Laid-open No. H11-249495).
Japanese Patent No. 3950635 discloses a static eliminator for a paper conveying apparatus which grounds the static generated from triboelectric charge between a roller and paper and in which a rotary shaft, which supports a paper conveying roller, is supported in a freely rotatable manner at the both ends by supporting members. In this technique, a conductive member for grounding contacts a portion of the peripheral surface of the rotary shaft (which includes an outer circumferential surface and an end face) via a static eliminating cloth, a conductive lubricant is applied to the surface of the static eliminating cloth that faces the rotary shaft made of a metal, and the surface of the conductive member for grounding, on which the static eliminating cloth is attached, has an exposed opposing surface where the conductive member for grounding does not contact the rotary shaft made of a metal (see FIGS. 2, 3, and 6 of Japanese Patent No. 3950635).
Japanese Patent No. 3938273 discloses a technology for conduction between a base and a support shaft in a photoreceptor; as shown in FIGS. 2 and 6, etc. of this patent document, in the photoreceptor, which includes a cylindrical conductive base with a photosensitive layer on the surface and an insulating flange press-fitted into the edge of the base and is configured to rotate around a metal support shaft attached to the center of the flange, a conductive member made of a conductive short fiber assembly is held between grounding plates with a guide hole bigger than a shaft hole made on the flange in the center and a plurality of contactors in contact with the inner surface of the base along the periphery, and the conductive member held between the grounding plates is fixed to the flange so as to bring the contactors into contact with the inner surface of the base, and an elastic plate-like pressing member is attached to a surface of the conductive member on the side opposite to a surface in contact with the support shaft, and then the tip of the conductive member fixed to the flange is brought into contact with the surface of the support shaft, thereby achieving conduction between the base and the support shaft.
However, in the technique disclosed in Japanese Patent Application Laid-open No. 2000-48873, the conductive shaft is pressed against the conductive cloth from above in a vertical direction by the weight of the conveying roller including the conductive shaft, so that electrical connection, e.g., grounding is achieved. Flexibility of the conductive cloth is not actively used in this technique.
In the technique disclosed in Japanese Patent Application Laid-open No. 2007-57945, the static eliminating cloth is attached to a member and comes into press contact with the member by being moved in synchronization with the member. Accordingly, flexibility of the conductive cloth is not actively used like in Japanese Patent Application Laid-open No. 2000-48873.
In the technique disclosed in Japanese Patent Application Laid-open No. 11-249495, a conductive cloth is not used and the electrical connection shaft made of a metal and the first leaf spring, which is also a metal member, slide on each other, so that abrasion occurs on either one or both of the members. For this reason, there have been problems, such as abnormal sound caused by abrasion, poor electrical connection caused by the oxidation of metal, and a large load caused by press contact. As measures against the sliding between metals, a conductive lubricant may be used to solve the above-mentioned problems. However, a conductive lubricant is scraped off at a contact point between metal members as sliding is done many times. Accordingly, although a conductive lubricant is a very effective measure at the early stage of sliding, it is not the fundamental solution.
Since an office machine, which is an electrophotographic image forming apparatus, such as a copying machine, a facsimile, or a printer, is used indoors, it is particularly required that no noise, no abnormal sound, is generated.
Also in the technology disclosed in Japanese Patent No. 3950635, as in Japanese Patent Application Laid-open No. 2000-48873, Japanese Patent Application Laid-open No. 2007-57945, and Japanese Patent Application Laid-open No. H11-249495, the flexibility of the conductive cloth is not actively utilized.
In the technology disclosed in Japanese Patent No. 3938273, as shown in FIG. 2, the conductive member (a conductive cloth) is bent by means of the flexibility so as to be in contact with the support shaft (a shaft) of the photoreceptor, however, it is a configuration that the shaft is inserted into the flange attached with the conductive cloth from outside to inside of the flange.
There is a need to achieve and provide a mechanism for electrification (grounding) of a rotating body used in any of an electrophotographic image forming apparatus, an electrostatic-recording image forming apparatus, and a magnetic-recording image forming apparatus, an image carrier unit, process cartridge, and image forming apparatus using the mechanism, and a method for electrifying the image carrier unit that are capable of resolving the above problems caused by sliding between metals and eliminating application of conductive lubricant in a simple, inexpensive, environmentally-friendly manner.